In this paper, the quality control in plasma spraying of chromium oxide ceramic coating on large area substrate is studied. This paper consists of three parts. Firstly, basic technical parameters are studied, for example, electric current, voltage, gas, powder, and spray distance. Secondly, the effect of dust from the spraying process on the coating quality is studied. Finally, the character of chromium oxide coating is researched. The results show that the dust from the spraying process greatly affects the coating quality. The effect of the following variables is examined: spray parameters, the powder size and distribution, and the substrate size. We have designed a set equipment to control the coating quality and the result was excellent. Now the equipment has been used in the production of anilox rollers and the patent has been applied. Meanwhile, we have devised a standard to determine the quality when spraying ceramic coating on large area substrate. The method has proved useful and efficient. Abstract only; no full-text paper available.

The present work deals with the application to actual in industrial conditions of the promising results of the study on adhesion, as presented at the previous edition of ITSC’2004 in Osaka, Japan. These industrial parts were typical of those produced in workshops for aircraft-aerospace, petro-chemical, printing works industries etc…. Thermal spray processing of industrial parts tested in this study are numerous, primarily air plasma spraying (APS), HVOF and conventional flame spray with or without remelting. Ultrasonic NDT facilities are now installed in an actual industrial workshop and show the reliability of the testing method and related results. For every tested part, digital ultrasonic testing was carried out to be compared to results from conventional adhesion tests according to EN 582 standard. U.T. results were quite in keeping with those from EN 582 testing. However, in addition, ultrasonic testing exhibited the any heterogeneity when existing, (local weak zones) at the coating-substrate interface. This resulted in easy discriminating of adhesive areas from cohesive areas. Results of this work obtained in a real workshop environment leaves promising expectations for ultrasonic testing to meet results from conventional EN 582 adhesion testing when applied to industrially-produced parts. Ultrasonic testing results in a low-cost NDT method which should compete with current high-cost control. Moreover, ultrasonic NDT looks more reliable in so far as the whole part can be controlled due to scanning of the whole surface.

The adhesion strength of a ceramic coating deposited through direct spraying on a roughened substrate is a key issue in the manufacture of high-quality coatings on industrial components. The purpose of this work was to develop a rapid and discerning procedure for establishing adhesion level of a ceramic coating on a metallic substrate. The Laser Shock Adhesion Test, namely LASAT, was successfully applied to ceramic coatings with irradiation impact on the metallic side. Suitable parameters were found to determine the LASAT adhesion threshold using a standard Nd:YAG laser source. With a laser-irradiated area of several millimetres in diameter, it allowed assessment of the coating threshold on several areas of a coated plate sample. A control procedure for a qualitative assessment of coating adhesion was developed. This testing procedure could be easily used in industry, with possible location of the LASAT unit near to the spraying booth, for a direct production control on coated sample to improve the tracability of manufactured parts. Additional work was carried out to investigate a quantitative approach of the LASAT test to ceramic coating. The purpose was to simulate the shock wave propagation with the RADIOSS® code (a 3D software originally developed for car crash simulation). This code was implemented to calculate the velocity of the material and corresponding pressure throughout the substrate and the coating during the shock wave release (less than 2 ms). Experimental VISAR profiles ('Velocity Interferometer System for Any Reflector') were monitored in the straight direction of the laser-irradiated area on the rear side. These experimental signals (velocity measures) of the ceramic coating could be fitted and compared with a fairly good agreement with simulated profiles obtained by RADIOSS®. This modelling work was the first step towards a more comprehensive coating adhesion strength calculation in the future.

In the field of thermal spraying a lot of things have been and still are happening concerning education and training of personnel. The education and training of thermal sprayers according EWF-Guideline is required frequently in combination of the international standard DIN EN ISO 14918 “Approval Testing of Thermal Sprayers” - especially in the German-language countries. Meanwhile about 13 ETS courses were held at the German Welding Institute. Also interested in the education and training of thermal sprayers are countries like Poland and China. In France thermal spray personnel was educated and trained in a company internal course. Sweden and Norway run ETS courses in cooperation. The EWF education and training course of the ETSS European Thermal Spraying Specialist will be offered by the German Welding Institute in Munich - SLV München - for the nineth time in October 2005. Since about 1993 European Committees of EWF (European Federation of Welding, Joining and Cutting) and CEN (European Committee or Standardization) worked out education and training guidelines and qualification standards of thermal spray supervising personnel and sprayers and established them step by step. The meanwhile created and internationally accepted EWF-education and training guidelines of supervising personnel and thermal spray workers involve also the new ISO standards of the Thermal Spraying Co-ordinator and the Approval Testing of Thermal Sprayers. The ISO personnel qualification and quality management standards result together with the EWF education and training guidelines in a sound QM-system, which meets the increased demands of trade and industry of high quality sprayed coating. Experiences in applying these guidelines and standards are introduced.

In this investigation, the concepts of fracture mechanics are put to use to determine the adhesion strength of WC-Co coatings on metal substrates. The paper explains how test samples are produced and describes the procedures used to obtain fracture mechanics data. Adhesion strength is determined based on local energy release rates (crack closure integral method) and is verified using a finite element model of the test sample. With this approach, the spraying parameters for WC-Co can be more precisely tuned than would be possible with a frontal pull test. Paper text in German.

This paper describes the equipment and procedures used to investigate the effects of the heat load on SOFC surfaces during vacuum plasma spraying. It explains how the authors used a vacuum-sealed IR camera to record thermographic images of the substrate surface as they sprayed different powders and as they varied the dc power, scanning speed, and stand-off distance of the plasma torch. The authors also studied the effect of different cooling methods, including conductive cooling from the backside via a water-cooled aluminum backplate and convective cooling from the front side with a nitrogen gas jet. Using the experimentally obtained data, the authors developed a thermal 3D model of the SOFC plasma spraying process that accounts for torch movements, substrate cooling, and layer growth. An outlook for future work is given expressing an intent to model stress fields within fuel cells during plasma spraying in order to simulate the development of residual stresses. Paper includes a German-language abstract.

This paper discusses the use of IR thermography in the development and control of thermal spraying processes. In the experiments, Al 2 O 3 layers are plasma sprayed on steel, aluminum, and glass substrates while recording surface temperatures. The measurements are then used to establish a correlation between temperature control and internal stress in the layer composite. The work shows that substrate preheating and torch kinematics have a significant effect on residual stress. Paper includes a German-language abstract.

Metallurgical powders can be characterized by different techniques including image analysis, laser particle size analysis, and various forms of sieve analysis. This paper evaluates a new method that uses a high-resolution slide scanner in combination with automated image analysis. The results obtained with this system are comparable to powder analysis via laser scattering and classical sieving techniques, but are more sensitive to changes in powder quality. Paper includes a German-language abstract.

This paper reviews the new DIN EN ISO personnel qualification and quality management standards and EWF training guidelines for European thermal sprayers. EWF education and training programs run for a period of three weeks, filling critical gaps in knowledge and experience. The primary aim of the ISO standards is to facilitate a reproducible process for spraying coatings of a consistent quality. Paper text in German.